This invention is concerned with improvements in or relating to blind riveting and is especially concerned with tools for use in setting the rivets of pull-through blind-riveting assemblies.
The expression "pull-through blind riveting" is used herein to denote a procedure in which a shank of a tubular rivet having a head at one end, assembled on a stem of a mandrel which has a head which is too large to pass through the rivet shank without deforming it, is inserted in a hole in a workpiece from one side, in such a manner that the head abuts the workpiece at said one side and the shank projects from the workpiece at the other side, and the rivet is set by pulling the mandrel stem at said one side of the workpiece while holding the head of the rivet against the workpiece whereby the mandrel head effects radial expansion of the rivet shank at the other side of the workpiece and is thereafter pulled right through the rivet.
It is customary in pull-through blind riveting to use a rivet-setting tool which has a mandrel with a long stem on which a number, for example 25, rivets are assembled, the rivets being set one after another upon reciprocation of the mandrel and forward feeding of the rivets up to the mandrel head. After all the rivets on the mandrel have been set, the mandrel is removed from the tool and reloaded with fresh rivets. It has also been proposed to provide a rivet-setting tool in which a long mandrel is held captive by two sets of gripping means, one of which serves to pull the mandrel stem, which can be released alternatively to allow the rivets fed to the tool one at a time to be fed forwardly along the mandrel stem. The use of a long mandrel not only involves the construction of a longer tool than might otherwise be necessary, but a mandrel to be used for setting successive rivets is in itself an expensive item, and the longer it is, the more costly it is to manufacture. Advancing of rivets along a mandrel stem in a tool to which they are fed one by one, the tool having jaws to grip and pull the mandrel stem, avoids having to remove the mandrel for reloading, but so far as we are aware, such proposals as have been made hitherto, have involved a construction of tool in which the jaws can be separated by a distance sufficient to allow passage therebetween of the rivets, that is to say, by much more than is necessary merely to release the grip of the jaws on the mandrel.